Method of and apparatus for multiple stage grinding



-March 21, 1933. F M|LLER 1,902,413

METHOD OF AND APPARATUS FOR MULTIPLE STAGE GRINDING Filed April 29, 19-31 3 Sheets-Sheet l I nueni'or: Ari'hur EJWjlZer,

A. F. MILLER March 21, 1933.

METHOD OF AND APPARATUS FOR MULTIPLE STAGE GRINDING s Sheets-Sheet 2 Filed April 29, 1931 Int/22107:

Ani'iz urEJliller,

A. F. MILLER March 21, 1933.

METHOD OF AND APPARATUS FOR MULTIPLE STAGE GRINDING Filed April 29. 1931 3 Sheets-Sheet 3 Inventor: .DZiZZer,

Patented Mar. 21 1933 UNITED STATES PATENT OFFICE ARTHUR F. MILLER, OF JACKSON, MICHIGAN, ASSIGNOR TO TRAYLOR ENGINEERING & MANUFACTURING COMPANY, OF ALLENTOWN, PENNSYLVANIA, A CORPORATION OF. DELAWARE METHOD OF AND APPARATUS FOR MULTIPLE STAGE GRINDING Application filed April 29,

My said invention relates to an improved method of multiple stage grinding or comminuting materials and apparatus for carrying out said method and of the general type disclosed in an application filed by me in the United States Patent ()llice on the 24th day ofApril, 1930, Serial Number 446.918.

The invention aims to provide a method and apparatus by which the grinding or comminuting may be effected with a minimum expenditure of power, and in a much more expeditious, economical and eflicient manner than by methods and apparatus of which I am aware. I

The invention also aims to provide a. meth- (id and apparatus of the three stage grinding type by which the material may be ground to extreme fineness and the fines removed at each stage thereby eliminating the cushioning action of the fine material in a subsequent mill stage or grinding compartment.

A further object is to provide a novel arrangement of multiple ball mill whereby an extremely fine and uniform product may be secured, and which will operate on closed circuits including separators or classifiers, whereby escape of dust is prevented.

Another object is to provide a novel arrangement of means for feeding separated comminutcd material needing further reduction through the periphery of the mill intermediate the ends thereof.

\Vith these and other objects in View the invention includes the novel method and apparatus hereinafter described and defined by the appended claims.

Figure 1 is a front elevation, largely of a conventional or diagrammatic nature, showing my novel apparatus, the mill being shown partly in section. I

Fig. 2 is an end elevation.

Fig.13 is an enlarged longitudinal section through the portion of the-mill tube or drum embodying my improved. intermediate feed. being a transverse section on line 3-3 of Fig. 4.

Fig. 4 is a section on line 44 of Fig. 3 partly broken away.

Fig. 5 is a detail view.

In proceeding according to my invention 1931. Serial No. 533,842.

I provide a ball or tube mill 1 which, except as hereinafter specified, may be of the ordinary or any desired construction.

t is provided. at opposite ends with hollow trunnions, through which material may be fed, and is divided into three mill compartments A, B and C, respectively, which may be regarded as first, second and third compartments in the order designated.

Compartments A and C are separated from each other by an imperforate partition 2, whereby they are isolated from each other, while compartments B and C are separated by a grated diaphragm 3 which permits fines to pass from the end compartment B into the third or intermediate compartment.

The mill tube/or drum-l may be rotated by any suitable means, as by gear 4 driven from any suitable source of power, not shown, and the material to be ground or comminuted may be fed to compartment A through hollow trunnion 1a from a. feed bin 5 or other suitable source by any desired form of feed means such as a table feeder which, as it is well known to those skilled in the art, as shown conventionally at 6.

Adjacent the partition 2 the annular wall of compartment A is provided with peripheral discharge openings a and compartment C is provided with similar discharge openings c, which openings are in communication with annular collecting chambers 7 and 8 respectively. v

The material ground in chamber orIcompartment A and passing through screen A into collecting chamber 7 is delivered therefrom through pipe 7a to the elevator 8 by which it is elevated to the distributing chutes 9 through which it passes to the separating means such as vibrating screens 10. These may be of the Hummer type which,'being well known, are shown in a conventional manner only.

These screens separate the ground mate- 9 rial into oversize and nnderslze, the over size being conveyed by means such as screw conveyor 11 to a discharge pipe 12 connecting' with the feed to compartment A and serving to return such oversize to said compartment for regrmdmg. The undersize 1s 5 partment C.

conveyed by means such as screw conveyor 13 to an elevator 14 which delivers it to conveyor 15 by which it is conveyed to air separator 16 of the type disclosed in my aforesaid application. This air separator separates the undersize into coarse and fine material.

.The coarse material is delivered by pipe 17 through hollow trunnion lb into grinding compartment B where it is further ground, the finely divided product passing through screen 3 into compartment C. The fine material from the air separator passes through pipe 18 into the'compartment C by means hereinafter more fully described and shown in detail in Figs. 3 and 4, being commingled in such passage with the fines passing from compartment B through the grate 3 and the commingled fines being ground to ultimate fineness in compartment C and being delivered through openings 0 into collecting chamber 8 and passing thence through pipe 8a to screw conveyor 19 by which it may be conveyed to any desired point.

In order to feed the fine material-delivered by pipe 18 through the peripheral wall of the mill I provide the following means. (See Figs. 3 and 4) -Encircling the drum or tube 1 and fast thereto is an annular casing 20 having an endless or annular opening or slot 20a in a side wall thereof and an inclined wall 206 adjacent said slotted side wall. Said slot is closed by a floating ring 21 supported and held thereagainst by suitable means such as inclined rod or link members 22 having their upper ends pivotally connected to the ring on opposite sides of the tube and their lower ends articulated to fixed supports 23. The lower end of the feed pipe passes through an opening in said floating ring at one side of the tube. I

The annular casing 20 is provided with a plurality of partition members 200 andopenmgs 1412 are provided through the annular wall of the tube or drum adjacent these partitions. As the material passes from pipe 18 into casing 20 it is deflected by the inclined wall 20?) into the path of the partitions 20c by which it\is elevated until it is in a position where it drops by gravity through the openings 1a: and into the interior of thedrum.

The tube or drum is' provided with a transverse diaphragm 24 having wear plates-25 on the side facing grinding'chamber C, this diaphragm being spaced from grate 3 to form a narrow transverse chamber 301: to receive the fines, which chamber communicates by central passage 24 a with chamber of com- Said fine receiving chamber is provided with radial partitions 26 which serve to lift the material until it is in position to flow by gravity into the chamber C ad acent the axis of the mill as indicated by the arrow Fig. 3.

Conduits 27 are provided leading from the openings 12; to points adjacent the axis of the mill whereby the fines supplied by pipe 18 are commingled with those from compartment B and pass together through the eye or opening in diaphragm 24.

In the operation of the mm the comminuting bodies or balls may be of successively reduced size and weight in the respective com pa rtmcnts, the largest in compartment A and the smallest in compartment C.

The sectional view, Fig. 3, istaken on the irregular line 33 of Fig. 4, and therefore partly along the conduits 27 extending radially inward from the annular chamber 20 to the eye of this transverse partition or diaphragm member, indicated generally by the character Bx, the section also being taken partly through the grating portion 3 of the partition and along the spaces 3: which convey the fines passing through the grating to the eye of this structureand into the intermediate compartment C. i

I claim: 1 v

1. The process of comminuting material which comprises (a) reducing the material by subjecting the same to'the action of comminuting means, (1)) separating the reduced product into undersize and oversize material,

(a) returning the oversize for further reduc-' tion by said means, (d) separating the undersize into fine and coarse material; (e) sub: 1

jecting the coarse material to the action of a second set of comminuting means to produce fine material, (f) and subjecting. the fine of the' undersize and the fine froms'aid second set of comminuting means to theaction of a third set of comminuting means.

2. The process of comminuting material which com rises reducing the material by" subjecting it to the action of comminuting means, separating the reduced product'into l undersize and oversize material, returning the oversize for further reduction by said comminuting means, separatin the undersize into fine and coarse material, subjecting the coarse material to the action of a second comminuting 'means'to produce fine material, commin ling said last nam'ed fine material with said first named fine material, and

subjecting said commingled fine material to I to produce fine material, commingling said last named fine material with said first named fine material, and subjecting said commingled fine material to the action of a third comminuting means.

4. The process of comminuting material which comprises (a) preliminarily reducing the material by subjecting the same to the action of comminuting means, (7)) separating the reduced material into undersize and oversize, (0) returning the oversize to said comminuting means, ((1) separating the undersize into relatively fine and coarse material, (6) delivering the said coarse material to a second comminuting means, and ('f) delivering the said fines from the second separation and the ultimate product of said second comminuting means to a third comminuting means.

5. The process of comminuting material which comprises (a) preliminarily reducing the material by subjecting the same to the action of comminuting means, (1)) separating the reduced material into undersize and oversize, (a) returning the oversize to said comminuting means, (d) pneumatically separating the undersize into relatively fine and coarse material, (6) delivering the said coarse material to a second comminuting means, and (f) delivering the said fines from the pneumatic separator andthe ultimate product of said second comminuting means to a third comminuting means.

6'. The process of comminuting material which comprises (a) preliminarily reducing the material by subjecting the same to the action of comminuting means, (b)v separating the reduced material into undersize and oversize, (c) returning the oversize to said comminuting means, ((1) pneumatically separating the undersize into relatively fine and coarse material, (0) delivering the said coarse material to a second comminuting means, and commingling the fines from said second separation and the fines from said second comminuting means and delivering them to a third comminuting means.

7. The process of comminuting material which comprises preliminari y reducing the material by subjecting the same to the action of relatively large and heavy comminuting bodies, separating the reduced material into undersize and oversize, returning the oversize for further reduction, separating the undersize into fine and coarse material, reducing thecoarse material by smaller and lighter comminuting bodies, commingling said fine material with the material comminuted by said second set of bodies, and subjecting said commingled material to the ac- 303 of still smaller and lighter comminuting 8. Apparatus of the class described com-- prising means for preliminarily reducing material, means for separat ng the material into undersize and oversize, means for returning theoversize to said'preliminary re- Y ducing means, means for separating the said fine material and subjecting it to further reductiom.

9. -\pparatus of the class described comprising means forprelin'iinarily reducing material, screen means for separating the reduced material into oversize and undersize, means for returning the oversize to said reducing means. means for pneumatically separating the undersize into coarse and fine material, means for further reducing said course material, and means for commingling said further reduced material and said fines and subjecting them to still further reduction. 7

10. In combination, a tube mill having three compartments, means for feeding material into an end compartment for preliminary reduetion, means for delivering reduced material from the periphery of said compartment, a separator receiving said reduced material and separating it into oversize and undersize, means for returning the oversize to said end compartment, means for separating the undersize into coarse and fine material. means for feeding the coarse material to another end compartment of the mill, means for passing the fines from said other end compartment into the intermediate compartment, *means for feeding the fines from the separator into the periphery of the intermediate compartment adjacent said other end compartment, and means for delivering ultimate product from said intermediate compartment.

11. In combination, a tube mill having feed inlets in its ends, an imperforate partition forming a preliminary reduction cham-- ber adjacent one end, a perforate partition adjacent the other end forming another reduction chamber, said partitions forminga third reduction chamber therebetween, and means for. feeding material into the periphcry of said third compartment adjacent said perforate partition, said mill having peripheral discharge outlets from said preliminary and final reduction compartments adjacent said imperforate partition.

12. In a comminuting 'mill, a rotary drum, means for introducing material into an end of the drum, and means for introducing material through the periphery of the drum comprising an annular casing. carried by said drum. said drum having ports communicating with said casing, said casing having an endless slot in its wall, a stationary floating V rharge it from the grating and from the an-.

. drum divided into three compartments,

ate chamber is adapted to make the finest reduction, means for feeding material into cud chambers, grating means separating the second end chamber from the intermediate chamber and through which grating the fines from the second chamber passes into the intermediate chamber, means for rotating the chambers, means for feeding material into the intermediate chamber comprising an annular chamber, having an annular opening, a fixed ring closing said annular opening and a conduit extending through said fixed plate and discharging into said annular chamber, and a conduit for delivering the material from said annular chamber into the intermediate compartment, substantially as described.

14. In apparatus accordin to claim 13, said diaphragm having a disc arge opening or eye at its central portion axially in line with the axis of the drum for the delivery of the fines from the second compartment and from the annular chamber into the intermediate chamber.

15. Apparatus according to claim 12 in which vanes rotating with the drum lift the material at the transverse diaphragm todisnular chamber into the intermediate compartment.

16. In combination in a comminuting mill, a drum having two compartments arranged coaxially, means for rotating said drum, means in the compartments for reducing the material, a diaphragm forming'the divison between the compartments, means for feeding material to the end of one compartment, said diaphragm being perforated for the passage of the material from the last mentioned compartment directly into the other compartment, means for feeding material through the periphery of the drum into said other compartment, said feed means commingling the material entering through the diaphragm with the material entering through the peripheryand having a common delivery into said other compartment substantially axially thereof, and means of discharge from said other compartment, substantially as described.

. 17. In combination in a ball mill, a drum divided into three compartments, means for feeding material into the end of the two outside compartments, and means for feeding material through the periphery of the intermediate compartment, means for delivering material from an end compartmentjnto the intermediate com artment, said delivery and the delivery 0 the material through the periphery taking place substantially at the axis of the said intermediate compartment, substantially as described.

18. In combination in a ball mill, a rotary means for feeding the material into the end compartments, means for feeding material through the periphery of the intermediate compartment at the end thereof where it joins one of the end compartments, and means for delivering the material from said end compartment into the intermediate compartment at the end thereof where the feeding delivery takes place, whereby the materials fed through said peripheral delivery, and the material received from the end compartment will commingle at one end of said intermediate compartment, and means of discharge at the other end of said intermediate cogipartment, substantially as described.

I n testimony whereof, I afiix my signature.

ARTHUR F. MILLER. 

